Quantum dots which are ultrafine particles having a particle size of 10 nm or less are excellent in confinement of carriers (electrons, holes), so that excitons can be easily generated by recombination of electrons-holes. For this reason, light emission from free excitons can be expected, and light emission having a high light-emission efficiency and a sharp light-emission spectrum can be realized. Also, because the quantum dots can be controlled in a wide wavelength range using the quantum size effect, a light-emitting element containing quantum dots in a light-emitting layer has been attracting attention and has been eagerly studied and developed in recent years.
For example, Patent Document 1 proposes a method of producing an electroluminescence (hereafter referred to as “EL”) element in which a light-emitting layer containing quantum dots is patterned by using the photolithography method, as shown in FIG. 8.
In this Patent Document 1, a first electrode layer 102 electrically insulated via an insulating layer 101 is formed on a substrate 103; a hole injection layer 104 is formed thereon; and a photoresist layer 105 is formed in a predetermined pattern so that the photoresist layer of a light-emitting region may be removed, as shown in FIG. 8(a).
Next, a light-emitting layer 106 is formed by using an application liquid containing quantum dots having a silane coupling agent coordinated thereto and a hole-transporting material, as shown in FIG. 8(b).
Next, the photoresist layer 105 is exposed via a photomask, developed thereafter with a photoresist developing liquid, and washed, whereby the remaining photoresist layer 105 is removed, and the light-emitting layer 106 on the photoresist layer 105 is lifted off, and thus a light-emitting layer 106a having a pattern form is formed, as shown in FIG. 8(c).
Finally, then, a second electrode layer 107 is formed on the light-emitting layer 106a, as shown in FIG. 8(d).
Also, Patent Document 2 proposes a method of producing an EL element in which a light-emitting layer containing quantum dots is patterned by using a layer in which the wettability changes by action of a photocatalyst accompanying energy radiation, as shown in FIG. 9.
In this Patent Document 2, a first electrode layer 112 electrically insulated via an insulating layer 111 is formed on a substrate 113, and a wettability changing layer 114 is formed thereon, as shown in FIG. 9(a). Here, the wettability changing layer 114 contains a photocatalyst and is constituted in such a manner that the wettability changes by energy radiation such as ultraviolet rays.
Next, ultraviolet rays are radiated onto the wettability changing layer 114 via a photomask. Then, by action of the photocatalyst contained in the wettability changing layer 114, the wettability changes in the irradiated part of the wettability changing layer 114 so that the contact angle to the liquid may decrease thereby to form a lyophilic region 115, and a liquid-repellent region 116 in which the wettability does not change is formed in the non-irradiated part, as shown in FIG. 9(b).
Then, when an application liquid containing quantum dots having a ligand such as a silane coupling agent coordinated thereto is applied onto the wettability layer 114, the application liquid is repelled in the liquid-repellent region 116 while the application liquid adheres in the lyophilic region 115, as shown in FIG. 9(c), whereby a light-emitting layer 117 is formed on the surface of the lyophilic region 115.
Finally, then, a second electrode layer 118 is formed on the light-emitting layer 117, as shown in FIG. 9(d).
Patent Document 1: Japanese Patent Application Laid-open (JP-A) No. 2009-87760 (claim 1, paragraph [0026], and FIG. 1)
Patent Document 2: Japanese Patent Application Laid-open (JP-A) No. 2009-87781 (claim 1, paragraphs [0034] to [0038], and FIG. 1)